zspot98

iTrader: (87)

I put a 224/228 cam in my car w/ LT's, 3600 stall and LS6 intake and am now getting about 13 mpg with normal driving in the city and was wondering if this is normal? It wasn't tuned by a professional, but my buddy is pretty knowledgeable when it comes to HPTuners and I've pulled the plugs and O2's since the install and it does not appear to be running rich. Any tuning suggestions or inputs on a fix for this problem. I know we had to adjust the TB blade for it to idle better, but I filled up my tank of Friday and only put 40 miles on the car and it's down to 3/4 of a tank. This seemed a little crazy to me. Any inputs would be greatly appreciated.

2xLS1

iTrader: (25)

The converter is probably hurting your mileage more than the cam. If most of your in town driving is at speeds where the 3600 converter is not locked, that will kill your mileage. Sometimes driving in 3rd where the converter will lock at a much lower mph instead of OD will help.

SgtB

iTrader: (3)

your converter not locking will cause DD mileage to go down but you just need to deal with it if you want a fast A4

Screamin_Z

iTrader: (2)

what they said. I have a 228R cam, stage 1+ LS6 heads, 30lb injectors, racetronix LS1/6 kit, and ALL bolt-ons...but I have a manual. I'm getting average 24mpg city/highway.

jimmyblue

iTrader: (11)

Another element is, even if the long tubes aren't making
your fuel trimming whacked, any air shoot-through to the
exhaust will make you trim toward the rich side to make
up for elevated exhaust oxygen content. That's a cam
overlap deal, you probably have a little. Idle and low
cruise are where you'd see it. It may not be anough to
foul plugs, you can still burn "clean" at (say) 13:1 actual
mixture. A wideband reading at idle would tell you about
the trim-point. Another issue is, the long tubes' thermal
shedding makes the sensors slower and the proportional
fueling then swings wider about the center; more time
in more nonideal mixture ranges makes worse fuel use.

But then, with a similar converter now and a smaller one
previously, I have seen 15, 16MPG mixed as a rule.

zspot98

iTrader: (87)

Thanks for all the input. It looks like this is something I'm just going to have to live with. I will try the driving in 3rd for awhile and see if that helps.

2xLS1

iTrader: (25)

Pay attention to the speeds lockup occurs in 3rd and OD. If you are above the 3rd L/O mph but below the OD L/U mph, use 3rd. If you are above the OD L/U mph, use OD. Mine locks around 30 in 3rd and 40 in OD. Your tuner can adjust those points as well.